1. Field of the Invention
The present invention relates to a process for developing silver halide black-and-white photographic sensitive materials and, particularly, to a development process which does not generate silver sludges even if a developing solution which contains sulfite in a high concentration or a silver halide solvent is used.
2. Description of the Prior Art
When processing image-wise exposed photographic materials comprising at least one silver halide layer, development is generally carried out in a presence of, for example, hydroquinone, catechol, aminophenol, phenylenediamine, pyrazolidone, reductone or hydroxylamine derivatives. The development is generally carried out in an alkaline medium, and the developing solution generally contains additives such as sulfites for stabilization, pH buffer materials, anti-fogging agents, and so forth. Particularly, in order to increase the stability of the developing solution, it is important to add sulfite in a high concentration. Furthermore, in order to obtain a special effect, the development of photographic materials is sometimes carried out in a presence of a silver halide solvent. For example, it has been known to add, as the silver halide solvent, divalent sulfur compounds, for example, mercapto compounds, thioethers or thioamides, thiocyanates, sulfites in a high concentration or thiosulfates. Developers containing the silver halide solvent have been used both as micrograin developers or mean grain developers (see Modern Photographic Processing, by Grant Haist, published by Wiley-Interscience Co., 1979, pp. 225-229). Another important embodiment of using the silver halide solvent is a one-bath development-fixing solution, which has been described in Monobath Manual, by G. Haist (published by Morgan Co., 1960).
The developing solution containing the silver halide solvent or the sulfite in a high concentration dissolves a comparatively large amount of silver salt from the silver salt layer of the photographic materials. The silver salt dissolved in the developing solution is then reduced by a developing agent to become finely-divided metallic silver, by which sludges are formed in said solution. Particularly, when developing by means of a conveyor type automatic development apparatus using a developing solution containing a large amount of silver halide solvent, deposition of sludges causes serious problems because a large amount of silver salt dissolves. Particularly, when processing at a high temperature, extreme deposition of sludges occurs. These sludges deposit as lumps on various parts of the conveyor type automatic development apparatus used for development, such as on rolls, belts, etc., to contaminate the surface of films or damage the films, by which quality of finished photographs deteriorates. Accordingly, it is important to prevent the silver contamination of films, particularly in photographic sensitive materials for printing.
Examples of known sludge preventing agents used for the above-described purpose include 2-mercapto-1,3,4-thiadiazoles (British Patent 940,169), 2-mercapto-1,3,4-oxadiazoles or 1-phenyl-5-mercaptotetrazole (U.S. Pat. No. 3,173,789), DL-6,8-dithiooctanoic acid (U.S. Pat. No. 3,318,701), o-mercaptobenzoic acid (British Pat. No. 1,144,481), aliphatic mercaptocarboxylic acids (U.S. Pat No. 3,628,955), L-thiazolidine-4-carboxylic acid (J. Photogr. Sci., Vol. 13, p. 233 (1965)), divalent sulfur compounds (Japanese Patent Application (OPI) No. 36029/77 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), 2-mercaptobenzoxazole and 2-mercaptobenzimidazole (Photogr. Sci. Eng., Vol. 20, p 220 (1976)), and so forth.
However, none of these compounds are completely satisfactory as sludge preventing agents in the photographic developing solutions, and particularly in developing solutions containing a compound which has a dissolving function with respect to silver halide, such as sulfite in a high concentration (e.g., in an amount of 13 g or more of sulfite per liter of developing solution, as mentioned hereinafter). Many mercapto compounds rapidly lose their sludge preventing function because of (1) air oxidation of the mercapto compounds and (2) reactions of disulfide compounds, which are formed by oxidation of the mercapto compounds, with sulfite ions. When a large amount of silver salt is dissolved, insoluble silver salts result, which contaminate the films, though the degree of contamination depends upon the amount present. Furthermore, the addition of a large amount of mercapto compounds sometimes inhibits the rate of the development. Moreover, some such compounds give off an unpleasant smell.
Further, since the above-described compounds have low water-solubility, it is difficult to add them in an amount necessary to prevent deposition of sludges.